The present invention relates generally to hoses and particularly to fuel transport hoses such as fuel filler and fuel filler neck hoses having reduced permeability to fuel vapors. More particularly, this invention relates to blends of fluorelastomer interpolymers with fluorothermoplastic interpolymers, and to the use of such blends as a barrier layer for fuel transport hoses to reduce the permeability of such hoses to fuel vapors.
Recent environmental regulations imposed on the automotive industry severely limit the amount of fuel vapor that can permeate from the fuel systems of motor vehicles. Choosing the right polymer to provide high performance, long service life, and reduced permeability of fuel in the fuel systems of motor vehicles while maintaining costs at an acceptable level has been more difficult for automotive designers than ever before. Typically, fuel transfer and fuel vapor hoses have been made of butadiene-acrylonitrile rubber as the tube, but such hoses have a high permeability to fuel. Other hoses have a fluoroelastomer as the inner wall surface layer of the hose, but such hoses have higher permeability to fuel vapors. Attempts to produce fuel transfer hoses with reduced permeability to fuel vapors have included the use of corrugated polyamide and fluorocarbon thermoplastic tubes. However, these structures are very expensive.
Other attempts to produce a fuel filler neck hose with reduced permeability to fuel vapors used a tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride terpolymer liner and a thicker layer of hexafluoropropylene-vinylidene fluoride copolymer or other suitable elastomer as the conductive inner part of the tube. See, for example, U.S. Pat. No. 4,606,952 to Sugimoto and U.S. Pat. No. 5,430,603 to Albino et al. Such hose structures have a tendency to wrinkle on the inner radius of the forming mandrel or pin causing a cosmetic defect.
Accordingly, there is a need for an improved fuel hose that meets present industry standards.
In accordance with the present invention a blend of a first fluorointerpolymer having elastomer characteristics and a second fluorointerpolymer having thermoplastic characteristics unexpectedly provides a composition which not only meets the low permeability standard for fuel vapor, but also is relatively inexpensive to produce, exhibits good service life and, when used in the manufacture of fuel transfer hoses, has a good push-on value, seals well, has good low temperature properties and resists kinking and wrinkling of the hose structure while being formed in conventional molding techniques.
In a first embodiment of the invention, a composition having improved fuel vapor barrier properties is provided. The composition comprises a blend of a first fluorointerpolymer which comprises a copolymer, terpolymer or mixture thereof formed by the copolymerization of two or more monomers selected from the group consisting of hexafluoropropylene, vinylidene fluoride and tetrafluoroethylene, and a second fluorointerpolymer which comprises a copolymer, terpolymer or mixture thereof formed by the copolymerization of two or more monomers selected from the group consisting of hexafluoropropylene-vinylidene fluoride and tetrafluoroethylene, wherein the first fluorointerpolymer exhibits elastomeric characteristics and said second fluorointerpolymer exhibits thermoplastic characteristics.
In a second embodiment of the invention, a hose having improved fuel vapor barrier properties is provided. The hose comprises a barrier layer comprising a blend of about 20 to 80 weight percent of a first fluorointerpolymer with about 80 to 20 weight percent of a second fluorointerpolymer, the first interpolymer comprising a copolymer, terpolymer or mixture thereof formed by the copolymerization of two or more monomers selected from the group consisting of hexafluoropropylene, vinylidene fluoride and tetrafluoroethylene, and the second fluorointerpolymer comprising a copolymer, terpolymer or mixture thereof formed by the copolymerization of two or more monomers selected from the group consisting of hexafluoropropylene, vinylidene fluoride and tetrafluoroethylene wherein the first fluorointerpolymer exhibits elastomeric characteristics and the second fluorointerpolymer exhibits thermoplastic characteristics. The hose not only exhibits reduced permeability to fuel vapors, but also avoids kinking and wrinkling in conventional molding techniques, provides extended service life, and is relatively inexpensive to produce.
In a first manifestation of the hose of the present invention, the hose structure comprises a conductive or non-conductive barrier layer comprising a blend of a first fluorointerpolymer having elastomer characteristics and a second fluorointerpolymer having thermoplastic characteristics; and a protective cover adjacent to and surrounding the conductive barrier layer.
In a second manifestation of the hose of the present invention, the hose structure comprises a conductive or non-conductive barrier layer comprising a blend of a first fluorointerpolymer having elastomeric characteristics and a second fluoro-interpolymer having thermoplastic characteristics as a barrier layer forming the interior wall of the hose; an elastomeric layer adjacent to and surrounding the outermost surface of the barrier layer; a reinforcing layer adjacent to and surrounding the outermost surface of the elastomeric layer; and a protective cover layer adjacent to and surrounding the outer surface of the reinforcing layer.
In a third manifestation of the invention, the hose structure comprises a conductive or non-conductive elastomeric layer which forms the interior surface of the hose; a barrier layer comprising a blend of a first fluorointerpolymer having elastomer characteristics adjacent to and surrounding the outermost surface of the first elastomeric layer; a reinforcing layer adjacent to and surrounding the elastomeric layer; and a protective cover layer adjacent to and surrounding the reinforcing layer.
In a fourth manifestation of the invention, the hose structure comprises a first conductive or non-conductive elastomer layer which forms the interior surface of the hose; a barrier layer comprising a blend of a first fluorointerpolymer having elastomer characteristics and a second fluorointerpolymer having thermoplastic characteristics adjacent to and surrounding the outer most surface of the first elastomeric layer; a second elastomeric layer adjacent to and surrounding the outermost surface of the barrier layer; a reinforcing layer adjacent to and surrounding the outermost surface of the second elastomeric layer; and a protective cover layer adjacent to and surrounding the reinforcing layer.
Surprisingly, the hoses of the invention reduce the permeability of hydrocarbon vapors, particularly fuel vapors from the hose to below proposed industry standards have good low temperature properties, have good push-on values, exhibit extended service life, and are relatively inexpensive to produce without any wrinkles caused by sharp turns, curves and bends during the formation of the hose on a forming mandrel or pins.
It is an object of the invention to provide a blend of a first fluorointerpolymer having elastomer characteristics and a second fluorointerpolymer having thermoplastic characteristics wherein the first fluorointerpolymer having elastomeric properties comprises a blend of a first fluorointerpolymer which comprises a copolymer, terpolymer or mixture thereof formed by the copolymerization of two or more monomers selected from the group consisting of hexafluoropropylene, vinylidene fluoride and tetrafluoroethylene, and a second fluorointerpolymer which comprises a copolymer, terpolymer or mixture thereof formed from the copolymerization of two or more monomers selected from the group consisting of hexafluoropropylene, vinylidene fluoride and tetrafluoroethylene, wherein the first fluorointerpolymer exhibits elastomeric characteristics and the second fluorointerpolymer exhibits thermoplastic characteristics. The blend, when employed as a barrier layer in fuel transport hoses, provides low permeability to hydrocarbon fuel vapors.
It is another object of the invention to provide a hydrocarbon-resistant hose such as a fuel transfer hose, e.g., fuel filler hose that satisfies the industry standards for permeability particularly with respect to fuel vapors, that avoids kinking and wrinkling in conventional molding techniques, that has an extended service life, and that is relatively inexpensive to produce.
Other objects and advantages of the invention will be apparent from the following description and the appended claims.